Inamura will be assessed during pre-season as Celtic “see where he’s at as a young player and then it’s whether he stays with the squad or whether he has to go out on loan”.
Inamura, “a young player full of promise and potential”, joins compatriots Daizen Maeda and Reo Hatate at Celtic Park, while Kyogo Furuhashi, Yuki Kobayashi, and Tomoki Iwata have also been at the Scottish champions in recent years.
All were signed by former boss Ange Postecoglou, who spent three-and-a-half years in charge of Yokohama F Marinos before his switch to Glasgow in June 2021.
Inamura has chosen to wear the number 25 donned by childhood idol Shunsuke Nakamura, who starred for Celtic between 2005 and 2009.
“Many Japanese players have had success at this club,” Inamura told CelticTV. “Across the world, this is a massive club and is really well known. I am truly excited to be joining Celtic. It’s a huge opportunity for me.
“So far, the current Japanese players have been performing at a high level. I think that is why there are expectations on Japanese players. I really want to live up to those expectations and do my best.
“Regarding Nakamura, I used to imitate his kicking style when I was a kid. He was one of my favourite players.”
Albirex sit second bottom of the J-League after 22 games following their 4-0 weekend defeat by eighth-placed Machida Zelvia.
Afterwards, Inamura announced it was his final game, telling the club website: “I am sorry to have made this decision when the team is in a difficult situation.
“I know not everyone will be happy to see me off, but I will fight with all my might so one day everyone will think this decision was the right one and feel proud.”